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pH (Urine)
Interpretive Summary
Description: The pH of urine is an index of acid-base balance but is not a reliable indicator of blood pH.
Decreased pH (Acidic)
Common Causes
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Metabolic acidosis
o Ethylene glycol intoxication
o Diabetic ketoacidosis
o Renal failure
o Lactic acidosis
o Addison’s disease
High protein or milk-based diet
Paradoxical aciduria (acid urine pH with metabolic alkalosis) due to severe vomiting
Uncommon Causes
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Medications or toxins
o Carbonic anhydrase inhibitors
o Salicylate
o Paraldehyde
o Methanol
o Urinary acidifiers
o Furosemide
Respiratory acidosis
Vomiting with chloride depletion or severe diarrhea
Proximal renal tubular acidosis with bicarbonate depletion
Fever, starvation, or prolonged exercise
Decreased serum potassium
Hydrogen production by bacteria
Related Findings
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Metabolic Acidosis
o Ethylene glycol intoxication
 Increased BUN, creatinine, phosphorus, anion gap
 Decreased calcium
 Calcium oxalate monohydrate crystalluria
o Diabetic ketoacidosis
 Increased blood glucose, BUN, creatinine, ALP, ALT
 Decreased sodium, TCO2, increased or decreased potassium
 Glucosuria and ketonuria
o Renal failure
 Increased BUN, creatinine, phosphorus
 Decreased TCO2
 Decreased urine specific gravity
o Lactic acidosis
 Increased sodium, chloride and TCO2
 Increased hematocrit
o Addison’s Disease
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pH (Urine)
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 Decreased sodium, albumin, cholesterol
 Increased potassium, BUN, creatinine
 Low urine specific gravity
Paradoxical aciduria (acid urine pH with metabolic alkalosis)
o Increased TCO2
o Decreased chloride, potassium
Increased pH (Alkaline)
Common Causes
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Recent meal (postprandial alkaline tide)
Artifact
o Delayed sample analysis (spontaneous degeneration of urea)
o Pigmenturia
Urinary tract infection (UTI) with urease-producing bacteria (Staphylococcus spp., Proteus spp.)
Uncommon Causes
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Metabolic alkalosis
Respiratory alkalosis
Proximal renal tubular acidosis (early) or distal renal tubular acidosis
Diets rich in vegetables and cereals
Related Findings
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Urinary tract infection with urease-producing bacteria
o Pyuria, hematuria, bacteriuria
o Positive urine culture with growth of Staphylococcus spp. or Proteus spp.
o +/- Struvite crystalluria
Additional Information
Physiology
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Urine pH is a measure of the hydrogen ion concentration in urine.
Urine pH is determined by the kidney's ability to regulate hydrogen ion and bicarbonate concentrations within the blood.
Normal urine pH in dogs and cats: 6.0-7.5
Urine pH is variable based on diet
o Cats and dogs usually have acidic urine
o Anorexia can cause an acidic urine
o Cats and dogs on vegetable-based diet may have an alkaline urine
References
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Latimer KS, Mahaffey EA, Prasse KW, eds. Duncan and Prasse's Veterinary Laboratory Medicine: Clinical Pathology,
4th ed. Ames, IA: Blackwell; 2003.
Stockham SL, Scott MA. Fundamentals of Veterinary Clinical Pathology, 2nd ed. Ames, IA: Blackwell; 2008.
Willard MD, Tvedten H, eds. Small Animal Clinical Diagnosis by Laboratory Methods, 4th ed. St. Louis, MO: Saunders;
2004.
Last updated 11/1/2013
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pH (Urine)
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